1. Field of the Invention
The present invention relates to a magnetooptical disc apparatus, which can erase and rewrite information on a disc-shaped magnetooptical recording medium and, more particularly, to a magnetooptical disc apparatus, which can be commonly used for magnetooptical recording media having different formats such as a magnetic field modulation type overwrite-capable magnetooptical recording medium, an optical modulation type magnetooptical recording medium, a ROM disc, or the like.
2. Related Background Art
When magnetooptical recording based on a magnetic field modulation method is to be performed, a magnetic head must be brought to a position close to a disc surface (recording film) of a magnetooptical recording medium in consideration of the relationship between a modulation frequency and a generated magnetic field, like in a case of a conventional induction type magnetic recording disc apparatus. Therefore, it is easiest and most effective to adopt a floating type slider, which utilizes air dynamic pressure effect generated upon rotation of a disc, in the magnetic head of the magnetic field modulation method. In this case, a sliding surface of the slider, and the opposing disc surface preferably has high surface precision and smoothness so as to maintain a stable floating state (a state keeping a predetermined gap).
However, in an optical modulation type (intensity modulation of a laser beam) magnetooptical recording medium or a ROM (a change in reflectance of emboss pits) disc, since no countermeasure taken in the above-mentioned floating type slider is taken on the disc surface side, a stable floating state cannot be obtained when the magnetic head is loaded with respect to the disc surface of the magnetooptical recording medium, thus causing damage to the disc surface (recording film) and the sliding surface of the floating type slider.
Therefore, in a magnetooptical disc apparatus having versatility for magnetooptical recording media of different modulation methods, when information is recorded/reproduced on/from a non-magnetic field modulation type magnetooptical recording medium, the magnetic head must be used by escaping it from a loading position with respect to the disc surface, as follows. As a conventional escaping mechanism for the magnetic head using the floating type slider, a mechanism employed in a magnetic field modulation type magnetooptical disc apparatus shown in FIGS. 1 to 3 is known.
In the magnetooptical disc apparatus shown in FIGS. 1 to 3, seek operations of both an optical head (optical pickup device) 103 and a magnetic head 104 carried on a carriage 102 are simultaneously performed by a seek motor (driving device) 101. The magnetic head 104 is attached to a floating type slider, and the slider is attached to a magnetic head pop-up mechanism 105 via a support beam. The pop-up mechanism is operated by a magnetic head escaping mechanism (to be described later), so that the magnetic head can approach/go away with respect to a disc surface of a magnetooptical recording medium 108.
In the magnetic head pop-up mechanism 105, a pivot member 111 is supported to be pivotal about a support shaft 112 as a pivot shaft arranged on the carriage 102, and the support beam is attached to the pivot member 111. In addition, an engaging contact portion 106 is arranged, and is biased downward by a pressing biasing member 107 to pivot the pivot member 111. As a result, the magnetic head 104 can be escaped or moved away from the disc surface. The vertical movement of the pressing biasing member 107 is controlled by a driving means such as a solenoid mechanism. A disc type detection sensor 115 and a disc cassette load/writing inhibition detection sensor 116 are arranged on a chassis of the magnetic disc apparatus, and are used in magnetic head escaping control to be described below.
More specifically, in a non-loading state of a disc cassette, no output signals are generated from the sensors 115 and 116. In this state, the driving means is inactive, and the pressing biasing member 107 is held at its lower position to press the engaging contact portion 106, and the magnetic head 104 is escaped above the disc surface, as shown in FIG. 1.
When a disc cassette is loaded, the sensor 116 detects it, and the sensor 115 detects a disc type detection portion 1100 (FIG. 4) provided on a disc cassette 110. The detection results are supplied to a control circuit. If the control circuit determines that a magnetic field modulation type overwrite-capable disc is loaded, it supplies a command signal to a driving circuit to enable the driving means. Thus, as shown in FIG. 2, the pressing biasing member 107 is moved upward, and is disengaged from the engaging contact portion 106. In this case, the pivot member 111 is pivoted about the support shaft 112 since it is biased by a spring (not shown) in a load direction of the magnetic head in the carriage 102. A locking member 109 for defining the load position of the magnetic head is arranged on the pivot member 111. When the locking member 109 is brought into contact with a locking portion 113 provided on the carriage 102 upon pivotal movement of the pivot member 111, the pivotal movement of the pivot member 111 is stopped at that position, and loading of the magnetic head 104 is completed. The magnetooptical recording medium 108 stored in the disc cassette 110 is rotated and scanned by a spindle motor 120, and is subjected to recording/reproduction upon radiation of a laser spot by the optical head 103 and application of a magnetic field by the magnetic head 104.
When the control circuit determines from the detection results of the sensors 116 and 115 that the loaded magnetooptical recording medium is, e.g., a ROM disc or an optical modulation type magnetooptical recording medium, it does not output a command signal to the driving circuit. Therefore, since the pressing biasing member 107 is kept at its lower position, as shown in FIG. 3, the magnetic head 104 is held at an unload position.
However, the above-mentioned conventional escaping mechanism suffers from the following drawbacks when a magnetooptical disc apparatus, which adopts this mechanism, is arranged to have the above-mentioned versatility. More specifically, the escaping mechanism adopted in this apparatus is subjected to two-way control, i.e., is controlled in correspondence with an escaping (unload) position upon loading/unloading of a disc cassette and a load position of the magnetic head to the disc surface of a magnetooptical recording medium. For this reason, the escaping amount is large, and a large-size driving means (e.g., a solenoid mechanism) for the escaping mechanism must be used. In addition, when a non-magnetic field modulation type magnetooptical recording medium is loaded, a pressing member (e.g., the above-mentioned pressing biasing member 107) must be allowed to extend from the chassis over the entire seek range so as to seek the magnetic head which is kept separated from the disc surface, thus disturbing the mounting space.